Direct injection of urine on a HPLC column-switching system for determination of D9-tetrahydrocannabinol-11-oic acid with both UV and electrochemical detection
Legend: Fig. 2. Chromatograms from the analysis of authentic urine samples, measured
concentrations of D9-tetrahydrocannabinol-11-oic acid (THC acid) a) 32ng/ml, b)
14ng/ml. A = zone trapped. Peaks: 1. THC